On Jun 26, 1:15 pm, "Wesley Furr" <wes...@megley.com> wrote: > How do you manage to replace those puny little surface-mount jobbies though? > Through-the-board electrolytics aren't a problem, I've done a number of them > over the years...
There are two types of surface mount capacitor on the boards. The first type are the tiny little "chips" that look a lot like surface mount resistors. These are ceramic surface mount capacitors and do not need to be replaced. I'm not sure if they have a practical lifetime limit. The other ones are the problem, the surface mount electrolytic capacitors. They look like tiny silver oil storage tanks. Little upright cyclinders. Apple typically used 47uF 16V caps all over the place plus a few other either 1 uF 50V, or 10uF <mumble>V. These are the ones that need to be replaced. There are a few boards with odd values like 22uF. The easiest way to remove them is to get two soldering pencils and apply one to each lead on the cap until the solder is fully melted and the capacitor will lift up without applying any substantial force. Getting impatient and forcing the cap up leads to lifted pads and torn traces. I use a pair of 15 watt soldering pencils from radio shack for this ( < $10 each) but 15 watts is a little underpowered. It takes a little longer than optimum to heat the caps enough to remove them. A pair of 25 watt or even 40 watt might be better. After removing them, apply some liquid solder flux (comes in a bottle) to the old solder and use desoldering braid and a soldering pencil to clean the remaining solder off of the copper pads. I find that the Chemtronics brand of desoldering braid (available at Digi-key) works the best for me. After removing the old solder, clean the board. I use a spray flux remover, but isopropyl alcohol works fine and even soapy water would do the trick. After cleaning, rinse the board with distilled water and let dry. To replace the caps, first "tin" one pad with a bit of solder. Tinning is just the act of melting a little solder onto the pad. Then place a cap on the pads (one tinned, one not) using a tweezers, and hold the cap down with a small flat head screwdriver. Then with the hand that is not holding the screwdriver, apply the soldering pencil to the tinned pad until that end of the cap sinks down to the pad. Be sure to heat both the pad and the terminal on the cap to solder melting temperature with the pencil. Proper heating of both surfaces is essential to good solder joints. Remove the soldering pencil. A few seconds later, remove the screwdriver. You now have a cap held down on one side. Solder the other side normally. Repeat until all the caps are replaced. This really isn't difficult. The place most folks run into trouble is in trying to remove the old caps with just one pencil. They get one side hot, then try to heat the other side, by which time the first side has cooled, and eventually, they either lift a cold side, tearing a pad or trace or bending something that shouldn't be bent, or they get the whole assembly so hot that again, they lift a pad or trace. Patience is also key. Very key. Essential. Jeff Walther -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to vintage-macs@googlegroups.com To leave this group, send email to vintage-macs+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/
